1. Field of the Invention
This invention relates to a fuel metering control system for an internal combustion engine.
2. Description of the Related Art
The PID control law is ordinarily used for fuel metering control for internal combustion engines. The control error between the desired value and the controlled variable (plant output) is multiplied by a P term (proportional term), an I term (integral term) and a D term (differential or derivative term) to obtain the feedback correction coefficient (feedback gain). In addition, it has recently been proposed to obtain the feedback correction coefficient by use of modern control theory or the like, as taught by Japanese Laid-Open Patent Application Hei 4(1992)-209,940.
When conducting feedback control based on modern control theory like an adaptive controller such that an air/fuel ratio or the quantity of fuel injection is brought to a desired value, using the amount of fuel injection as the manipulated variable, at the time that the engine operation has just shifted from an open-loop control region to a feedback control region, a spike may sometimes occur in the detected air/fuel ratio, unless internal variables of the controller are properly determined, thereby degrading the control stability.